The present invention broadly relates to, aeronautical engineering and specifically to rotors of aircraft, for example, for use in helicopters and manufacture of same.
Coaxial lifting systems are known. For example, a coaxial lifting system contains a reducing gear with two shafts rotating in opposite directions on which the rotors are mounted, two swashplates connected to one another by tie rods and movable in the axial direction, which are kinematically linked to guides of blades and to a summing leverage control system of the collective and differential pitch. Levers of the summing control system are respectively connected to the lower swashplate and the internal tie rod. Control of the upper rotor is accomplished by use of a slide block mounted on the shaft of the upper rotor movably along its axis and kinematically coupled to the internal tie rod the upper swashplate and the blade guides. The internal tie rod is lengthened and fitted with a yoke which is mounted at its free end and kinematically linked to a slide block implemented in the form of a sliding hub which is connected to the shaft of the upper rotor on the axis whereof there is mounted a frame with facility for wobbling, a lifting lever link connected to the facility for wobbling relative to the latter, where the direction of the axes of the wobbling of the frame and the levers are mutually perpendicular (Patent RF No. 120627, publ. Sep. 27, 2012).
A disadvantage of the known solution is the complexity of the design as a result of the large number of hinged joints linking the slide block located below the upper rotor to the upper swashplate and the blade guides of the upper rotor and also as a result of the presence of a complex summing mechanism for controlling the collective and differential pitch which has a large number of levers. The presence of a large number of kinematically interacting elements reduces the reliability of the system and increases its weight.
One attempted technical solution embodies a coaxial lifting system containing a reducing gear with two shafts rotating in opposite directions on which are mounted rotor hubs, two swashplates that are connected to one another and movable in the axial direction, and which are kinematically linked to guides of blades, and to the summing lever system of the collective and differential pitch. The rotor hubs are made as two-blade with total horizontal hinges. The guides of the blades of the lower rotor hub are connected to the lower swashplate by rockers mounted on a slide block located below the lower rotor hub, and the guides of the blades of the upper rotor hub are connected by tie rods directly to the upper swashplate. The radii of the guides on the upper rotor hub are smaller than on the lower rotor hub, and the lower swashplate and the slide block are kinematically linked to the control system of the collective and differential pitch by a summing lever system in which one lever is connected by one arm to the differential pitch control and the second is connected to the slide block and the second lever which is articulated to the first is connected by its arms to the collective pitch control and to the slide block of the lower swashplate (Patent RF No. 2307766, publ. Oct. 10, 2007).
A disadvantage of this system is its low reliability due to the complex design since the summing lever system connected to the slide block and the lower swashplate is over-saturated with hinged-articulated links with bearing nodes mounted in a restricted kinematic space on mutually mobile slide blocks. In addition, the presence of a large number of kinematically interacting elements increases its weight.